Photoresist composition and, used in the photoresist composition, low-molecular compound and high-molecular compound

ABSTRACT

A high-molecular compound and a low-molecular compound or both having an alkali-soluble site (i) wherein at least a part of the alkali-soluble site (i) is protected with (ii) a halogen atom-containing acetal type acid-dissociative, dissolution inhibiting group, as well as a photoresist composition comprising the same. The photoresist composition is highly stable during storage and can give a resist pattern excellent in sectional rectangular shape and having high transparency to an exposure light, particularly a light having a wavelength of 300 nm or less.

TECHNICAL FIELD

The present invention relates to a photoresist composition used inpatterning of a semiconductor integrated circuit by lithography, alow-molecular compound and a high-molecular compound preferable forconstituting the photoresist composition, and in particular to aphotoresist composition excellent in transparency in fine patterningwith a light source having a wavelength of 300 nm or less, especially aKrF, ArF, or F₂ excimer laser, particularly the F₂ excimer laser, and toa low-molecular compound and a high-molecular compound preferable forconstituting the photoresist composition.

BACKGROUND ART

Fine patterning of semiconductor integrated circuits has been achievedby progress in photolithography and its related technologies. As is wellknown, this photolithography is supported mainly by two technologies.One technology is related to the exposure light wavelength and numericalaperture of a miniaturized projection light exposure device called astepper or a scanner, and the other is concerned with resistcharacteristics composed chiefly of transfer resolution of a photoresistcomposition onto which a mask pattern is to be transferred by theminiaturized projection light exposure device. By the combined actionsof the two technologies, the processing accuracy of a semiconductorintegrated circuit pattern by photolithography has been improved.

The wavelength of a light source used in the miniaturized projectionlight exposure device becomes shorter and shorter in accepting a demandfor higher resolution of circuit patterns. Generally, g-line of 436 nmin a main spectrum of a mercury lamp is used for a resist resolution ofabout 0.5 μm; i-line of 365 nm in a main spectrum of the mercury lamp isused for a resolution of about 0.5 to 0.30 am; a KrF excimer laser lightof 248 nm is used for a resolution of about 0.30 to 0.15 μm; an ArFexcimer laser light of 193 nm is used for a resolution of about 0.15 μmor less; and use of an F₂ excimer laser light of 157 nm, an Ar₂ excimerlaser light of 126 nm, and an EUV (extreme ultraviolet, wavelength 13nm) light is examined for further fine patterning.

In view of the photoresist composition, on one hand, a combinationthereof with an organic or inorganic anti-reflective coating film or alighting system has been devised, and in lithography using a KrF excimerlaser light, the life of a photoresist for KrF is prolonged, and aphotoresist composition in consideration with about 110 nm of below λ/2is under development. In lithography using an ArF excimer laser light,it is desired to provide photoresist compositions for ArF preferable formass production in the future of those for a node of about 90 nm orless. Lithography using the F₂ excimer laser attracts attention astechnology taking responsibility for fine processing at 65 nm or less inthe future, and a photoresist composition which can be appliedsatisfactorily to lithography using the F₂ excimer laser is beingdeveloped.

As is well known in lithography, a photoresist layer applied on alaminate semiconductor substrate is irradiated with a short-wavelengthlight (light exposure) via a mask reflecting a negative or positivepattern of a semiconductor integrated circuit pattern to be realized.The photoresist composition contains, as a main component, aphotosensitive polymer which upon reacting with the irradiation light,will be rendered insoluble (negative) or soluble (positive) with analkali, and after exposure to the patterning light, is subjected to heat(post exposure bake, also referred to as “PEB”) for securing thereaction of the resist layer by light exposure, and then subjected todevelopment to remove soluble parts, whereby a photoresist pattern layeraccurately reflecting the circuit pattern to be realized is formed onthe laminate semiconductor substrate. Thereafter, the patternedphotoresist layer may be sufficiently cured by heating (post bake) tomake it durable to etching in a next step. In the etching step, thesurface layer or the top layer of the laminate semiconductor substrateis subjected to dry-etching along the pattern with the patternedphotoresist layer as a mask.

Accordingly, the major properties required for the photoresistcomposition are to achieve resolution, and the first property forachieving this resolution is “transparency to irradiation light” bywhich the patterning irradiation light reaches not only the surface ofthe resist layer but also the bottom at the side of the substratethereby sufficiently photosensitizing the irradiated portion as a wholein such thickness as to include the bottom. By securing thistransparency, it is possible to realize a pattern of high resolution oran excellent pattern having a sectional shape in a rectangular shapehaving almost the same width from the top to base after patterningdevelopment.

To secure this transparency is also important for development of aresist composition coping with a shorter wavelength of irradiationlight. For the transparency to exposure light, the development of a basepolymer itself is advancing, and several kinds of excellent polymershave been proposed. As promising base polymers, fluorine-containingnorbornene polymers (Non-patent document 1 (Proceedings of SPIE, Vol.3999, (2000) pp357-364)), polymers in Patent document 1 (Internationalpublication WO 00/67072 Pamphlet) and Patent document 5 (Japanese PatentApplication Laid-open No. 2002-333715), fluorine-containing monocyclicpolymers (Patent document 2 (Japanese Patent Application Laid-open No.2002-90997)), and polymers in Patent document 3 (Internationalpublication WO 02/64648 Pamphlet), Patent document 4 (Internationalpublication WO 02/65212 Pamphlet), and Non-patent document 2 (Shun-ichiKodama, et al., “Synthesis of Novel Fluoropolymer for 157 nmPhotoresists by Cyclo-polymerization” Proceedings of SPIE, Vol. 4690,(2000) pp76-83) have been reported.

These polymers, as can be confirmed or estimated from descriptions inthese documents, are determined to be capable of securing transparencyat the practical level to a light having a wavelength of 300 nm or less.

DISCLOSURE OF INVENTION

The above-described polymer improves transparency by introducing afluorine atom into a main chain or a side chain of its base resin. Theacid-dissociative, dissolution inhibiting group (hereinafter referred tosometimes as a protective group) includes halogen atom-free groups, forexample a tertiary alkyl ester type acid-dissociative, dissolutioninhibiting group such as a general tert-butyl ester group, anether-based acid-dissociative, dissolution inhibiting group such as atert-butyl ether group, and an acetal type acid-dissociative,dissolution inhibiting group such as a tetrahydropyranyl ether group ora 1-ethoxyethoxy group.

However, these dissolution inhibiting groups, particularly a carbonylgroup of an ester, have absorption at 157 nm and are thus poor intransparency. An ether and acetate, though not having such absorption,are still desired to improve transparency.

The present invention has been achieved in view of these circumstances,and the object of the invention is to provide a photoresist compositionexcellent in resolution and having high transparency to an exposurelight, particularly a light having a wavelength of 300 nm or less and alow-molecular compound and a high-molecular compound for obtaining thephotoresist composition.

To solve the problems, the present inventors made extensive study, andas a result, they found:

(1) To obtain transparency in the photoresist composition particularlyto an ArF or F₂ excimer laser light, the introduction of fluorine atomsinto its base resin component is effective, and the introduction offluorine atoms into a main chain or a side chain of polymerizable unitsof the base resin is proposed as shown in the above-described polymer.However, when fluorine atoms are to be introduced into a main chain or aside chain of the resin, there is a limit to the amount of fluorineatoms which can be easily introduced, and for increasing the amount offluorine atoms introduced, further complicated reaction is necessary.For controlling the alkali solubility of the base resin component, afluorine atom can be introduced into an acid-dissociative, dissolutioninhibiting group (protective group) modified by its soluble terminalsite thereby easily introducing the fluorine atom into the base resin tofurther improve the transparency of the resin component to an exposurelight.

(2) The protective group, owing to its role, will be eliminated from thebase resin component in a step of exposing the resist to light. As aresult, the fluorine atom in the protective group does not remain in thebase resin component, but this is not problematic because it is enoughfor the transparency of the resin achieved by fluorine atoms to bemaintained until light exposure is completed. The physical and chemicalproperties of the resin may be influenced when a large amount offluorine atoms are contained in the resin, and thus the system whereinfluorine atoms introduced in excess for merely achieving transparencyare removed after light exposure would rather be considered desirable.

The present invention has been achieved on the basis of such finding.That is, the photoresist composition of the present invention comprises:(A) a base resin component having alkali-solubility changed by theaction of an acid; and (B) an acid generator, wherein the base resincomponent (A) comprises a compound having an alkali-soluble site (i), atleast a part of the alkali-soluble site (i) is protected with (ii) ahalogen atom-containing acetal type dissolution inhibiting group, andthe dissolution inhibiting group (ii) is a group dissociable from thealkali-soluble site (i) by an acid.

The low-molecular compound for photoresist according to the presentinvention is a low-molecular compound for an acid-dissociative,dissolution inhibiting agent contained in a photoresist compositiongenerating an acid by light exposure and changing solubility in analkaline solution by the action of the acid to form a pattern, whereinthe low-molecular compound has an alkali-soluble site (i), at least apart of the alkali-soluble site (i) is protected with (ii) a halogenatom-containing acetal type dissolution inhibiting group, and thedissolution inhibiting group (ii) is a group dissociable from thealkali-soluble site (i) by an acid.

The high-molecular compound for photoresist according to the presentinvention is a high-molecular compound for a base resin componentconstituting a photoresist composition generating an acid by lightexposure and changing alkali-solubility by the action of the acid toform a pattern, wherein the high-molecular compound has analkali-soluble site (i), at least a part of the alkali-soluble site (i)is protected with (ii) a halogen atom-containing acetal type dissolutioninhibiting group, and the dissolution inhibiting group (ii) is a groupdissociable from the alkali-soluble site (i) by an acid.

In the present invention, the low-molecular compound, the high-molecularcompound, and the resin composition comprising at least one kind ofthese compounds can achieve the following excellent effects.

In the present invention, the high-molecular compound has aweight-average molecular weight of 3000 to 80000, preferably 5000 to50000.

In the present invention, the low-molecular compound has aweight-average molecular weight of 500 to 3000, preferably 1000 to 3000.

That is, when a fluorine atom is used as a halogen atom in a protectivegroup in the present invention, the fluorine atom can, without relyingon complex reaction, be introduced easily into a base resin component ofthe photoresist composition, to further improve the transparency of theresin component to a light having a wavelength of 300 nm or less.Particularly, the resist composition, as compared with a conventionalresist composition free of halogen in its protective group, can achievea significant improvement in transparency to an exposure lightparticularly using an F₂ excimer laser.

It is considered that the elimination of the protective group in thepresent invention is suppressed because the group contains an electronattractive halogen. By using this protective group whose elimination issuppressed, the light sensitivity in the vicinity of the surface of theresist layer can be near to the light sensitivity of a deep part of theresist layer, and as a result, easy resolution of a line and spaceresist pattern having a narrow space between lines can be expected.

In addition, the following effects can also be expected:

(1) The halogen atom-containing acetal type acid-dissociative,dissolution inhibiting group used in the present invention has highertransparency than that of the halogen-containing ester typeacid-dissociative, dissolution inhibiting group, and can thus realizehigher transparency than by the conventional material.

(2) The storage stability of the photoresist composition can be improvedbecause the elimination of the protective group can be suppressed byincorporation of the halogen.

(3) A bromine atom can be used as the halogen in the protective group toimprove the light sensitivity of a resist composition for exposure to anelectron beam or X-ray as a light source.

(4) Allowance in establishing regulatory factors such as depth of focusin the light exposure process can be increased.

(5) The resistance to etching of a resist film can be improved due tothe presence of the halogen atom.

(6) A cyclic group can be introduced into the protective group. In thiscase, the cyclic group can have a double bond, and this double bond canbe utilized to introduce a hydroxyl group via an epoxy group to improvethe hydrophilicity of the resist composition and the adhesion thereof toa substrate.

BEST MODE(S) FOR CARRYING OUT THE INVENTION

As described above, the present invention is characterized in that anyone of a high-molecular compound and a low-molecular compound or bothhaving an alkali-soluble site (i), wherein at least a part of thealkali-soluble site (i) is protected with (ii) a halogen atom-containingacetal type acid-dissociative, dissolution inhibiting group, is used asa constituent element of the photoresist composition.

In such constitution, the alkali-soluble site (i) is known asexemplified by the above non-patent documents and patent documents orfrom the previously proposed KrF resist, ArF resist and F₂ resist. Suchan alkali-soluble site includes, but is not limited to, an alcoholichydroxyl group, a phenolic hydroxyl group, and a carboxyl group. In thepresent invention, the alkali-soluble site is desirably at least onemember selected from an alcoholic hydroxyl group, a phenolic hydroxylgroup, and a hydroxyl group of a carboxyl group. Especially, analcoholic hydroxyl group or a fluorine-containing alcoholic hydroxylgroup is preferable because of its high transparency and suitable alkalisolubility.

The halogen atom-containing acetal type acid-dissociative, dissolutioninhibiting group (ii) is desirably a group represented by the followinggeneral formula (1):—O—C(R¹)(R²)—O—R³  (1)wherein R¹ and R² independently represent a hydrogen atom or a loweralkyl group, and R³ represents a halogen-containing substituted orunsubstituted hydrocarbon group.

A substituent group may or may not be present in the constitution, andthe substituent group when present is preferably a polar group such as ahydroxyl group or lactone group in order to increase affinity for aresist solvent, increase affinity for an alkali developing solution, andachieve excellent adhesion to a substrate. For F₂ excimer laser light, ahydroxyl group is particularly preferable because it has excellenttransparency.

The hydrocarbon group includes linear, branched, or cyclic saturatedaliphatic or unsaturated aliphatic hydrocarbon groups having 1 to 20carbon atoms. In particular, 1 to 16 carbon atoms, preferably 1 to 12carbon atoms of linear, branched, or cyclic saturated aliphatic orunsaturated aliphatic hydrocarbon groups are industrially preferable.

The hydrocarbon carbon group includes a methyl group, ethyl group,n-propyl group, isopropyl group, n-butyl group, isobutyl group, n-pentylgroup, cyclopentyl group, methyl cyclopentyl group, ethyl cyclopentylgroup, n-hexyl group, cyclohexyl group, methyl cyclohexyl group, ethylcyclohexyl group, heptyl group, octyl group, nonyl group, decanyl group,dodecanyl group, and groups wherein one hydrogen atom was removed frombicycloalkane, bicyloalkene, tricycloalkane, tetracycloalkane, methylbicycloalkane, methyl bicycloalkene, methyl tricycloalkane, methyltetracycloalkane, ethyl bicycloalkane, ethyl bicycloalkene, ethyltricycloalkane, or ethyl tetracycloalkane.

Specific examples of the cyclic hydrocarbon group include groups whereinone hydrogen atom was removed from adamantane, norbornane, norbornene,methyl norbornane, ethyl norbornane, methyl norbornene, ethylnorbornene, isobornane, tricyclodecane, or tetracyclododecane. Suchpolycyclic group can be selected from a large number of groups proposedin ArF resist. Among these, an adamantyl group, norbonyl group,norbornenyl group, methyl norbornyl group, ethyl norbornyl group, methylnorbornenyl group, ethyl norbornenyl group, and tetracyclododecanylgroup are industrially preferable.

The positions and the number of halogen atoms and the chemical formulaare not particularly limited in the above constitution, and one or morehalogen atoms or lower perhalogenoalkyl groups such as a trifluoromethylgroup, perfluoroethyl group, and perfluorobutyl group may be bonded tothe R³.

It is desired for excellent acid dissociation and from an industrialviewpoint that R³ in the general formula (1) is a group represented bythe following general formula (2):—[C(R⁵)(R⁶)]_(n)—R⁴  (2)wherein R⁴ represents a halogen-containing linear or cyclic hydrocarbongroup, R⁵ and R⁶ independently represent a hydrogen atom or a loweralkyl group, and n is 0 or an integer of 1 to 3.

Particularly, n is preferably 0 or 1 since the effect of electronattraction of the halogen atom can be easily utilized and the glasstransition point of the high-molecular compound having such group ishigh. Examples of R¹, R², R⁵, and R⁶ include a hydrogen atom and loweralkyl groups having carbon atoms of 1 to 5 such as a methyl group, ethylgroup, propyl group, isopropyl group, and butyl group. It isparticularly preferable that R¹, R², R⁵, and R⁶ are simultaneouslyhydrogen atoms.

For excellent acid dissociation and from an industrial viewpoint, theposition to which the halogen atom or the halogenoalkyl group is bondedis desirably the second or third position relative to the carbon atom(carbon atom to which R⁵ and R⁶ are bonded) adjacent to R⁴.

The halogen-containing linear or cyclic hydrocarbon group includes ahalogen-containing linear alkyl group, a halogen-containing cyclic alkylgroup, and a halogen-containing cyclic alkenyl group. The cyclic alkylgroup, linear alkyl group, and alkenyl group may be those mentioned withrespect to R³ above. Particularly, a 1-halogen-substituted linear loweralkyl group, a halogen-containing norbornyl group, and ahalogen-containing norbornenyl group are more excellent in aciddissociation and industrially suitable. The halogen-containingnorbornenyl group has a double bond, and this double bond can beutilized to introduce a hydroxyl group via an epoxy group to improve thehydrophilicity of the resist composition and the adhesion thereof to asubstrate.

The halogen includes fluorine, chlorine, bromine, and iodine, amongwhich a fluorine atom can be used to improve transparency to exposurelight, while bromine can achieve higher sensitivity, and thus thefluorine or bromine atom is preferable. Especially, the fluorine atom ismost preferable.

The acetal type acid-dissociative, dissolution inhibiting group includesa tetrahydropyranyl group, 1-ethoxyethyl group, 1-ethoxymethyl group,methoxymethyl group, methoxyethoxymethyl group, norbornyl methoxymethylgroup, and norbornenyl methoxymethyl group. In the present invention,the acetal type acid-dissociative, dissolution inhibiting group intowhich one or more halogen atoms or haloalkyl groups were introduced isused.

The low-molecular compound preferable as the acid-dissociative,dissolution inhibiting agent contained in the photoresist composition ofthe present invention includes, for example, low-molecular compoundswherein at least a part of alkali-soluble sites such as an alcoholichydroxyl group, a phenolic hydroxyl group, and a hydroxyl group of acarboxyl group are protected with the above-mentioned “acetal typeacid-dissociative group containing one or more halogen atoms”.

Such compounds include, for example, compounds represented by thefollowing general formulae (3) and (4):

wherein R¹¹ represents a hydrogen atom, an alkyl group, an alkoxylgroup, or a fluorine atom, R²² represents a halogen atom-containingacetal type acid-dissociative, dissolution inhibiting group, A is—C(C_(n)F_(2n+1))(C_(m)F_(2m+1))—O—CO—,—C(C_(n)F_(2n+1))(C_(m)F_(2m+1))—, or —O—CO—, and each of n, m, p, and qis independently an integer of 1 to 4.

The halogen atom-containing acetal type acid-dissociative, dissolutioninhibiting group is the one described above.

Specific examples of the compounds represented by the above generalformula include compounds represented by the following chemical formulae(5) to (8):

The low-molecular compound used in the acid-dissociative, dissolutioninhibiting agent contained in the photoresist composition, when shown ina state before addition of a protective group, is usefully a compoundrepresented by the following formula 4A:

The dissolution inhibiting agent composed of this low-molecular compoundcan be used to suppress the phenomenon of a reduction in a resist filmby an alkali developing solution.

The high-molecular compound (A) as the base resin component is ahigh-molecular compound composed of the polymerizable units representedby formulae 5A and 6A below, wherein at least a part of alkali-solublesites is protected with the above-mentioned “acetal typeacid-dissociative group containing one or more halogen atoms”, or ahigh-molecular compound composed of the polymerizable units representedby the formulae 5A and 6A and other polymerizable units copolymerizablewith said polymerizable units, wherein at least a part of alkali-solublesites is protected with the above-mentioned “acetal typeacid-dissociative group containing one or more halogen atoms”.

The high-molecular compounds represented by the formulae 5A and 6A aboveare known. However, the compounds wherein at least a part of alkalisoluble groups, that is, a fluorine alcohol, a carboxylic acid, aphenolic hydroxyl group, etc. are replaced by the “halogenatom-containing acetal type acid-dissociative, dissolution inhibitinggroup” in the present invention are not known.

In the present invention, a polymer comprising alkali-solubleconstitutional units (a1) each comprising an alicyclic group having both(i) a fluorine atom or a fluoroalkyl group and (ii) an alcoholichydroxyl group, wherein at least a part of the alcoholic hydroxyl groupis replaced by the halogen atom-containing acetal typeacid-dissociative, dissolution inhibiting group and changesalkali-solubility by the action of an acid is preferable because theeffect of the part of the protective group in the present invention issignificantly excellent to improve transparency.

The polymer (A′) before substitution with the “halogen atom-containingacetal type acid-dissociative, dissolution inhibiting group” is known asdescribed in the patent documents 1, 3, and 4 or in the non-patentdocument 2.

However, the compounds comprising the halogen atom-containing acetaltype acid-dissociative, dissolution inhibiting group introduced into theabove polymer are novel and not known hitherto. The polymer (A′) is notlimited insofar as it is a polymer comprising alkali-solubleconstitutional units (a1) each comprising an alicyclic group having both(i) a fluorine atom or a fluoroalkyl group and (ii) an alcoholichydroxyl group, wherein the polymer changes alkali-solubility by theaction of an acid.

The phrase “changes alkali-solubility by the action of an acid” refersto a change in a light-exposed portion of the polymer, wherein when thealkali-solubility of the exposed portion is increased, the exposedportion becomes alkali-soluble and hence the resist composition can beused as a positive resist, while when the alkali-solubility of theexposed portion is decreased, the exposed portion becomesalkali-insoluble and hence the resist composition can be used as anegative resist.

The alkali-soluble constitutional units (a1) each comprising analicyclic group having both (i) a fluorine atom or a fluoroalkyl groupand (ii) an alcoholic hydroxyl group may be constitutional units with anorganic group having both the groups (i) and (ii) bonded to thealicyclic group therein.

The alicyclic group can be exemplified by groups wherein one or morehydrogen atoms were removed from a monocyclic or polycyclic hydrocarbonsuch as cyclopentane, cyclohexane, bicycloalkane, tricycloalkane, ortetracycloalkane.

Specific examples of the polycyclic hydrocarbon include groups whereinone or more hydrogen atoms were removed from polycycloalkane such asadamantane, norbornane, isobornane, tricyclodecane, ortetracyclododecane.

Among these groups, groups derived from cyclopentane, cyclohexane, ornorbornane by removing hydrogen atom(s) are industrially preferable.

Examples of the fluorine atom or fluoroalkyl group (i) include afluorine atom and lower alkyl groups having part or all of theirhydrogen atoms replaced by fluorine atom(s). Specific examples include atrifluoromethyl group, a pentafluoroethyl group, a heptafluoropropylgroup, and a nonafluorobutyl group, among which a fluorine atom and atrifluoromethyl group are industrially preferable.

The alcoholic hydroxyl group (ii) may be either a single hydroxyl groupor an alcoholic hydroxyl group-containing alkyloxy group, an alcoholichydroxyl group-containing alkyloxyalkyl group, or an alcoholic hydroxylgroup-containing alkyl group, such as an alkyloxy group, alkyloxyalkylgroup, or alkyl group having a hydroxyl group. Examples of the alkyloxygroup, alkyloxyalkyl group, or alkyl group include lower alkyloxygroups, lower-alkyloxy-lower-alkyl groups, and lower alkyl groups.

Specific examples of the lower alkyloxy groups include a methyloxygroup, an ethyloxy group, a propyloxy group, and a butyloxy group;specific examples of the lower-alkyloxy-lower-alkyl groups include amethyloxymethyl group, an ethyloxymethyl group, a propyloxymethyl group,and a butyloxymethyl group; and specific examples of the lower alkylgroups include a methyl group, an ethyl group, a propyl group, and abutyl group.

In the alcoholic hydroxyl group-containing alkyloxy group, alcoholichydroxyl group-containing alkyloxyalkyl group, or alcoholic hydroxylgroup-containing alkyl group (ii), the alkyloxy group, alkyloxyalkylgroup, or alkyl group may have part or all of its hydrogen atomsreplaced by fluorine atom(s). It is preferred that the alcoholichydroxyl group-containing alkyloxy group or the alcoholic hydroxylgroup-containing alkyloxyalkyl group has part of the hydrogen atoms inits alkyloxy moiety replaced by fluorine atom(s), or the alcoholichydroxyl group-containing alkyl group has part of the hydrogen atoms inthe alkyl moiety replaced by fluorine atom(s), that is, preferredexamples include an alcoholic hydroxyl group-containing fluoroalkyloxygroup, an alcoholic hydroxyl group-containing fluoroalkyloxyalkyl group,and an alcoholic hydroxyl group-containing fluoroalkyl group.

Examples of the alcoholic hydroxyl group-containing fluoroalkyloxygroups include a (HO)C(CF₃)₂CH₂O— group, a2-bis(trifluoromethyl)-2-hydroxy-ethyloxy group, a (HO)C(CF₃)₂CH₂CH₂O—group, and a 3-bis(trifluoromethyl)-3 hydroxypropyloxy group; examplesof the alcoholic hydroxyl group-containing fluoroalkyloxyalkyl groupsinclude a (HO)C(CF₃)₂CH₂O—CH₂— group and a (HO)C(CF₃)₂CH₂CH₂O—CH₂—group; and examples of the alcoholic hydroxyl group-containingfluoroalkyl groups include a (HO)C(CF₃)₂CH₂— group, a2-bis(trifluoromethyl)-2 hydroxy-ethyl group, a (HO)C(CF₃)₂CH₂CH₂—group, and a 3-bis(trifluoromethyl)-3-hydroxypropyl group.

The groups (i) and (ii) may be directly bonded to the alicyclic group.Because of excellency in transparency, in alkali-solubility, and inresistance to dry etching, and easy industrial availability, theconstitutional unit (a1) is particularly preferably an unit representedby the general formula (9) below, which is formed by cleaving a doublebond of norbornene ring to which the alcoholic hydroxyl group-containingfluoroalkyloxy group, the alcoholic hydroxyl group-containingfluoroalkyloxyalkyl group, or the alcoholic hydroxyl group-containingfluoroalkyl group is bonded.

wherein Z represents an oxygen atom, an oxymethylene group (—O(CH₂)—),or a single bond, and n′ and m′ independently represent an integer of 1to 5.

Polymer units used in combination with the unit (a1) are notparticularly limited, and those conventionally known can be used. Whenthe resin composition is used as a positive-working polymer (A′-1)having alkali-solubility increased by the action of an acid, theconstitutional unit (a2) derived from a known (meth)acrylic ester havingan acid-dissociative, dissolution inhibiting group is preferred becauseof excellent resolution.

Examples of the constitutional unit (a2) include constitutional unitsderived from a tertiary alkyl ester of (meth)acrylic acid, such astert-butyl (meth)acrylate or tert-amyl (meth)acrylate.

The polymer (A′) may be a polymer (A′-2) having alkali-solubilityincreased by the action of an acid and further comprising afluoroalkylene constitutional unit (a3) for improving the transparencyof the polymer. By incorporation of the constitutional unit (a3), thetransparency of the polymer is further improved. The constitutional unit(a3) is preferably a unit derived from tetrafluoroethylene.

The general formulae (10) and (11) representing the polymers (A′-1) and(A′-2) respectively are shown below.

wherein Z, n′, and m′ are as defined in the general formula (9), R³³represents a hydrogen atom or a methyl group, and R⁴⁴ represents anacid-dissociative, dissolution inhibiting group.

wherein Z, n′, m′, R³³, and R⁴⁴ are as defined in the general formula(10).

The polymer (A′-1) and (A′-2) containing the general formula (8) havedifferent structural formulae, and may have the following constitutionalunit falling under the concept of the polymer having alkali-solubilitychanged by the action of an acid, comprising the alkali-solubleconstitutional unit (a1) containing an alicyclic group having both (i) afluorine atom or a fluoroalkyl group and (ii) an alcoholic hydroxylgroup.

That is, in the constitutional unit (a1), the fluorine atom orfluoroalkyl group (i) and the alcoholic hydroxyl group (ii) are bondedrespectively to the alicyclic group constituting a main chain.

The fluorine atom or fluoroalkyl group (i) includes those describedabove. The alcoholic hydroxyl group (ii) is a single hydroxyl group.

The polymer (A′) having such units is described in the patent document 3or 4 or the non-patent document 4, and is formed by cyclopolymerizationof a diene compound having a hydroxyl group and a fluorine atom. Thediene compound is preferably heptadiene easily forming a polymer havinga 5- or 6-membered ring excellent in transparency and resistance to dryetching, and the most preferable in industry is a polymer formed bycyclopolymerization of1,1,2,3,3-pentafluoro-4-trifluoromethyl-4-hydroxy-1,6-heptadiene(CF₂═CFCF₂C(CF₃)(OH)CH₂CH═CH₂).

When the resin composition is used as a positive-working polymer (A′-3)having alkali-solubility increased by the action of an acid, a hydrogenatom of its alcoholic hydroxyl group should be replaced by the “halogenatom-containing acetal type acid-dissociative, dissolution inhibitinggroup”.

The halogen atom-containing acetal type acid-dissociative, dissolutioninhibiting group includes those described above.

The degree of replacement of all hydroxyl groups thereby is in the rangeof 10 to 60%, preferably 14 to 55%, in order to achieve excellentpattern formability, adhesiveness, and resolution.

The general formula (12) representing the polymer (A′-3) is shown below:

wherein R⁵⁵ represents a hydrogen atom or a halogen atom-containingacetal type acid-dissociative, dissolution inhibiting group, and each ofx and y is 10 to 50 mol %.

The polymer (A′) can be synthesized by a known method, for example, amethod described in the patent document 1, 3, or 4 or the non-patentdocument 2. The polystyrene-equivalent, weight-average molecular weightof the resin in the component (A), as determined by GPC, is notparticularly limited, but is preferably 5000 to 80000, more preferably8000 to 50000. The degree of dispersion (Mw/Mn) is about 1.0 to 5.0,preferably 2.5 or less.

The polymer (A) may be comprised of one or more kinds of resins, forexample, a mixture of two or more resins selected from the (A′-1),(A′-2), and (A′-3) whose hydrogen atoms are replaced by halogenatom-containing acetal type acid-dissociative, dissolution inhibitinggroups, and may further contain another resin conventionally known forphotoresist composition.

The method of introducing the above-described protective group isdescribed. The compound represented by the following formula 11A can bedeprotected by an acid.

The compound represented by the formula 11A above can be obtained byreacting the chloromethyl ether compound obtained by the reaction in theformula 12A, with a compound represented by the following formula 13A.

In the present invention, a halogen atom-containing alcohol compound isused as a starting material to synthesize the corresponding chloromethylether derivative which is then reacted with a low-molecular orhigh-molecular compound having an alkali-soluble group to give theobjective compound. The compound can be used in a resist material torealize the dissolution inhibition thereof in an alkali developingsolution before light exposure and exhibition of alkali solubility withde-protection (in the case of a positive resist) in a post-exposureheating step.

The acid generator (B) used in the photoresist composition of thepresent invention can be selected suitably from arbitrary compoundsgenerating an acid upon irradiation with radiation rays. Various acidgenerators have been proposed, and especially preferred are onium saltssuch as diphenyliodonium trifluoromethanesulfonate,(4-methoxyphenyl)phenyliodonium trifluoromethanesulfonate,bis(p-tert-butylphenyl)iodonium trifluoromethanesulfonate,triphenylsulfonium trifluoromethanesulfonate,(4-methoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,(4-methylphenyl)diphenylsulfonium nonafluorobutanesulfonate,(p-tert-butylphenyl)diphenylsulfonium trifluoromethanesulfonate,diphenyliodonium nonafluorobutanesulfonate,bis(p-tert-butylphenyl)iodonium nonafluorobutanesulfonate, andtriphenylsulfonium nonafluorobutanesulfonate (TPS-PFBS). Among these,preferred are sulfonium salts comprising a fluoroalkylsulfonic acid ionas anion since they have appropriate acid strength and diffusionproperties in the resist film. The acid generators may be used singly oras a mixture of two or more thereof. The amount of the acid generatorincorporated is for example 0.5 to 30 parts by weight relative to 100parts by weight of the resin component. When the amount is smaller thanthis range, the formation of a latent image may be unsatisfactory, andwhen the amount is larger, the resistant resist composition may be poorin storage stability.

Next, the nitrogen-containing compound (C) added if necessary to theresist composition of the second aspect of the present invention isdescribed.

(Nitrogen-Containing Compound (C))

It has been known that a nitrogen-containing compound is incorporated ina small amount as an acid diffusion-preventing agent into the chemicallyamplified resist composition. In the present invention, such a knownnitrogen-containing compound can be added. Examples of thenitrogen-containing compounds include amines and ammonium salts.

Examples of the amines include aliphatic secondary amines such asdiethylamine, dipropylamine, dibutylamine, and dipentylamine; aliphatictertiary amines such as trimethylamine, triethylamine, tripropylamine,tributylamine, tripentylamine, N,N-dimethylpropylamine,N-ethyl-N-methylbutylamine, trihexylamine, triheptylamine,trioctylamine, tridecanylamine, tridodecylamine, andtritetradecanylamine, wherein the three alkyl groups bonded to nitrogenin the trialkylamines may be the same or different; tertiaryalkanolamines such as N,N-dimethylmonoethanolamine, triisopropanolamine,N,N-diethylmonoethanolamine, triethanolamine, and tributanolamine; andaromatic tertiary amines such as N,N-dimethylaniline,N,N-diethylaniline, N-ethyl-N-methylaniline, N,N-dimethyltoluidine,N-methyldiphenylamine, N-ethyldiphenylamine, and triphenylamine.

Examples of the ammonium salts include salts of quaternary alkylammoniumion such as ammonium ion, tetramethylammonium ion, tetraethylammoniumion, tetrapropylammonium ion, tetrabutylammonium ion, ortetrapentylammonium ion, and ion of an organic carboxylic acid having ahydroxyl group, such as lactic acid.

Among these, lower tertiary alkanolamines such as triethanolamine,triisopropanolamine, and tributanolamine, and trialkylamines having 6 to15 carbon atoms, such as trihexylamine, triheptylamine, trioctylamine,tridecanylamine, tridodecylamine, and tritetradecanylamine arepreferable to achieve an excellent effect of suppressing the reductionin a film on the top of a fine resist pattern.

The nitrogen-containing compound (C) is used usually in the range of0.01 to 2 parts by weight relative to 100 parts by weight of the polymercomponent (A). When the amount of the compound (C) is smaller than thisrange, it is not possible to achieve an effect of improving the shape ofa pattern by the effect of preventing the diffusion of an acid generatedupon exposure to light, while when the amount is too large, thediffusion of an acid is significantly suppressed to deteriorate exposuresensitivity disadvantageously.

In the present invention, an organic carboxylic acid, an oxo-acid ofphosphorus, or a derivative thereof can be further contained as anarbitrary component for the purpose of preventing the deterioration insensitivity caused by adding the nitrogen-containing component (C).

As the organic carboxylic acid, for example, malonic acid, citric acid,malic acid, succinic acid, benzoic acid, or salicylic acid is preferred.

Examples of the oxo-acids of phosphorus and derivatives thereof includephosphoric acid and derivatives thereof, for example, esters such asdi-n-butyl phosphate, and diphenyl phosphate; phosphonic acid andderivatives thereof such as esters, for example, dimethyl phosphonate,di-n-butyl phosphonate, phenylphosphonic acid, diphenyl phosphonate, anddibenzyl phosphonate; and phosphinic acid and derivatives thereof suchas esters, for example, phosphinic acid and phenylphosphinic acid, amongwhich phosphonic acid is preferable. The organic carboxylic acid,oxo-acid of phosphorus, or derivative component is used in an amount of0.01 to 5.0 parts by weight relative to 100 parts by weight of the resincomponent (A).

The resist composition in the second aspect of the present invention isused in the form of a uniform solution obtained by dissolving the resincomponent (A), the acid generator (B), the nitrogen-containing component(C), and an arbitrary component further added if necessary, in anorganic solvent. Specific examples of the organic solvent includeketones such as acetone, methyl ethyl ketone, cyclohexanone, methylisoamyl ketone, and 2-heptanone; polyhydric alcohols and derivativesthereof, such as monomethyl ether, monoethyl ether, monopropyl ether,monobutyl ether, or monophenyl ether of ethylene glycol, ethylene glycolmonoacetate, diethylene glycol, diethylene glycol monoacetate, propyleneglycol, propylene glycol monoacetate, dipropylene glycol, or dipropyleneglycol monoacetate; cyclic ethers such as dioxane; and esters such asmethyl lactate, ethyl lactate, methyl acetate, ethyl acetate, butylacetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, andethyl ethoxypropionate. These organic solvents may be used singly or asa mixed solvent of two or more thereof. Especially preferred arepropylene glycol monomethyl ether acetate (PGMEA) and ethyl lactate(EL).

The amount of the organic solvent is adjusted so that the resistcomposition can have a concentration applicable to a substrate or thelike to form a resist film.

An additive miscible with the composition, for example, a knowndissolution inhibiting agent, an additional resin for improving theperformance of the resist film, or a surfactant, a plasticizer, astabilizer, a coloring agent, or a halation preventing agent forimproving the coating properties can be further added if necessary tothe resist composition of the present invention.

The resist composition of the present invention is used in aconventional lithographic process to form a resist pattern. In thisprocess, the photoresist composition is applied by rotational coatingonto a substrate and dried to form a resist film. The resist film isthen exposed selectively via a mask pattern and then subjected topost-exposure heating. Finally, the resist film can be developed with anaqueous alkali solution to form a resist pattern. Further, post baketreatment may be conducted if necessary. The light source is notlimited, and far ultraviolet light, specifically an electron beam, asoft X-ray, or an X-ray such as an ArF excimer laser, an F₂ excimerlaser, an EUV (extreme ultraviolet) light, etc. can be used.Particularly, the F₂ excimer laser is preferable.

The conditions, that is, the number of revolutions of the resistcoating, the prebake temperature, the exposure conditions, the postexposure bake conditions, and the alkaline development conditions may bethose conventionally used. Specifically, the number of revolutions isabout 2000 rpm, specifically about 1200 to 3500 rpm, and the prebaketemperature is in the range of 70 to 130° C., thus forming a resist filmhaving a thickness of 80 to 250 nm. Exposure may be conducted through amask. As a mask in the selective exposure, a general binary mask isused. As the mask, a phase-shifting mask may be used. The post exposurebake temperature is in the range of from 90 to 140° C., and alkalidevelopment conditions are such that development is conducted using 1 to5 wt % TMAH (tetramethylammonium hydroxide) developer solution at 23° C.for 15 to 90 seconds, followed by rinsing with water.

EXAMPLES

Examples of the present invention will be explained below. Note that theExamples merely exemplify the invention preferably, and do not limit it.

(Synthesis of Chloromethyl Ether Compounds)

The method of synthesizing 1-monochloromethoxy-2-monofluoroethane(compound 1), 2-(chloromethoxymethyl)-2-trifluoromethyl norbornane(compound 2), 2-(chloromethoxymethyl)-2-trifluoromethyl norbornene(compound 3) is described in more detail.

Paraformaldehyde was added to 1 equivalent of 2-monofluoroethanol or2-(trifluoromethyl)bicycle[2,2,1]heptane-2-methanol, or2-(trifluoromethyl) bicycle[2,2,1]heptene-2-methanol, and 3 equivalentsof hydrogen chloride gas were blown into it, and the mixture was reactedat 40 to 100° C. After the reaction was finished, the product wasdistilled away under reduced pressure to give compounds 1 to 3.

(Introduction of the Chloromethyl Ether Compound into a High-MolecularCompound)

The chloromethyl ether compounds were introduced into resins 1 and 2described below synthesized by radical polymerization and additionpolymerization, to give resins 3 to 12 described below.

Resin Synthesis Example 1

10.0 g of resin 1 (weight−average molecular weight=7500, degree ofdispersion (Mw/Mn)=1.74) was dissolved in 100 mL of tetrahydrofuran, and0.32 g of sodium hydride was added thereto. The mixture was stirred atroom temperature until the solution became uniform, and then 0.83 g ofthe above compound 1 was added dropwise thereto. After stirring at roomtemperature for 12 hours, the precipitated salt was filtered off. Theresulting filtrate was dropped into 1 L of water. The precipitated resinwas separated by filtration, dried under reduced pressure, dissolved intetrahydrofuran, and dropped into 1 L of n-heptane. The precipitatedresin was separated by filtration and dried under reduced pressure togive white powder resin. The yield was 7.4 g. This resin is referred toas resin 3. The resin 3 had a weight-average molecular weight of 7800, adegree of dispersion (Mw/Mn) of 1.82, and a protection degree of 19%.

Resin Synthesis Example 2

10.0 g of the above resin 1 was dissolved in 100 mL of tetrahydrofuran,and 0.64 g of sodium hydride was added thereto. The mixture was stirredat room temperature until the solution became uniform, and then 1.66 gof the above compound 1 was added dropwise thereto. After stirring atroom temperature for 12 hours, the precipitated salt was filtered off.The resulting filtrate was dropped into 1 L of water. The precipitatedresin was separated by filtration, dried under reduced pressure,dissolved in tetrahydrofuran, and dropped into 1 L n-heptane. Theprecipitated resin was separated by filtration and dried under reducedpressure to give white powder resin. The yield was 9.3 g. This resin isreferred to as resin 4. The resin 4 had a weight-average molecularweight of 7700, a degree of dispersion (Mw/Mn) of 1.97, and a protectiondegree of 38%.

Resin Synthesis Example 3

10.0 g of the above resin 1 was dissolved in 100 mL of tetrahydrofuran,and 0.96 g of sodium hydride was added thereto. The mixture was stirredat room temperature until the solution became uniform, and then 2.49 gof the above compound 1 was added dropwise thereto. After stirring atroom temperature for 12 hours, the precipitated salt was filtered off.The resulting filtrate was dropped into 1 L of water. The precipitatedresin was separated by filtration, dried under reduced pressure,dissolved in tetrahydrofuran, and dropped into 1 L of n-heptane. Theprecipitated resin was separated by filtration and dried under reducedpressure to give white powder resin. The yield was 9.3 g. This resin isreferred to as resin 5. The resin 5 had a weight-average molecularweight of 7400, a degree of dispersion (Mw/Mn) of 2.02, and a protectiondegree of 56%.

Resin Synthesis Example 4

10.0 g of the above resin 1 was dissolved in 100 mL of tetrahydrofuran,and 0.32 g of sodium hydride was added thereto. The mixture was stirredat room temperature until the solution became uniform, and then 1.74 gof the above compound 2 was added dropwise thereto. After stirring atroom temperature for 12 hours, the precipitated salt was filtered off.The resulting filtrate was dropped into 1 L of water. The precipitatedresin was separated by filtration, dried under reduced pressure,dissolved in tetrahydrofuran, and dropped into 1 L of n-heptane. Theprecipitated resin was separated by filtration and dried under reducedpressure to give white powder resin. The yield was 8.6 g. This resin isreferred to as resin 6. The resin 6 had a weight-average molecularweight of 8700, a degree of dispersion (Mw/Mn) of 1.72, and a protectiondegree of 18%.

Resin Synthesis Example 5

10.0 g of the above resin 1 was dissolved in 100 mL of tetrahydrofuran,and 0.64 g of sodium hydride was added thereto. The mixture was stirredat room temperature until the solution became uniform, and then 3.48 gof the above compound 2 was added dropwise thereto. After stirring atroom temperature for 12 hours, the precipitated salt was filtered off.The resulting filtrate was dropped into 1 L of water. The precipitatedresin was separated by filtration, dried under reduced pressure,dissolved in tetrahydrofuran, and dropped into 1 L of n-heptane. Theprecipitated resin was separated by filtration and dried under reducedpressure to give white powder resin. The yield was 9.5 g. This resin isreferred to as resin 7. The resin 7 had a weight-average molecularweight of 10800, a degree of dispersion (Mw/Mn) of 1.82, and aprotection degree of 37%.

Resin Synthesis Example 6

10.0 g of the above resin 1 was dissolved in 100 mL of tetrahydrofuran,and 0.96 g of sodium hydride was added thereto. The mixture was stirredat room temperature until the solution became uniform, and then 5.22 gof the above compound 2 was added dropwise thereto. After stirring atroom temperature for 12 hours, the precipitated salt was filtered off.The resulting filtrate was dropped into 1 L of water. The precipitatedresin was separated by filtration, dried under reduced pressure,dissolved in tetrahydrofuran, and dropped into 1 L of n-heptane. Theprecipitated resin was separated by filtration and dried under reducedpressure to give white powder resin. The yield was 10.5 g. This resin isreferred to as resin 8. The resin 8 had a weight-average molecularweight of 9300, a degree of dispersion (Mw/Mn) of 1.85, and a protectiondegree of 53%.

Resin Synthesis Example 7

10.0 g of the above resin 2 (weight-average molecular weight=27600,degree of dispersion (Mw/Mn)=2.41) was dissolved in 100 mL oftetrahydrofuran, and 0.24 g of sodium hydride was added thereto. Themixture was stirred at room temperature until the solution becameuniform, and then 1.35 g of the above compound 2 was added dropwisethereto. After stirring at room temperature for 12 hours, theprecipitated salt was filtered off. The resulting filtrate was droppedinto 1 L of water. The precipitated resin was separated by filtration,dried under reduced pressure, dissolved in tetrahydrofuran, and droppedinto 1 L of n-heptane. The precipitated resin was separated byfiltration and dried under reduced pressure to give white powder resin.The yield was 9.0 g. This resin is referred to as resin 9. The resin 9had a weight-average molecular weight of 30800, a degree of dispersion(Mw/Mn) of 2.15, and a protection degree of 14%.

Resin Synthesis Example 8

10.0 g of the above resin 1 was dissolved in 100 mL of tetrahydrofuran,and 0.32 g of sodium hydride was added thereto. The mixture was stirredat room temperature until the solution became uniform, and then 1.73 gof the compound 3 was added dropwise thereto. After stirring at roomtemperature for 12 hours, the precipitated salt was filtered off. Theresulting filtrate was dropped into 1 L of water. The precipitated resinwas separated by filtration, dried under reduced pressure, dissolved intetrahydrofuran, and dropped into 1 L of n-heptane. The precipitatedresin was separated by filtration and dried under reduced pressure togive white powder resin. The yield was 9.5 g. This resin is referred toas resin 10. The resin 10 had a weight-average molecular weight of11300, a degree of dispersion (Mw/Mn) of 1.94, and a protection degreeof 20%.

Resin Synthesis Example 9

10.0 g of the above resin 1 was dissolved in 100 mL of tetrahydrofuran,and 0.64 g of sodium hydride was added thereto. The mixture was stirredat room temperature until the solution became uniform, and then 3.46 gof the compound 3 was added dropwise thereto. After stirring at roomtemperature for 12 hours, the precipitated salt was filtered off. Theresulting filtrate was dropped into 1 L of water. The precipitated resinwas separated by filtration, dried under reduced pressure, dissolved intetrahydrofuran, and dropped into 1 L of n-heptane. The precipitatedresin was separated by filtration and dried under reduced pressure togive white powder resin. The yield was 9.2 g. This resin is referred toas resin 11. The resin 11 had a weight-average molecular weight of 9000,a degree of dispersion (Mw/Mn) of 2.01, and a protection degree of 37%.

Resin Synthesis Example 10

10.0 g of the above resin 1 was dissolved in 100 mL of tetrahydrofuran,and 0.96 g of sodium hydride was added thereto. The mixture was stirredat room temperature until the solution became uniform, and then 5.19 gof the compound 3 was added dropwise thereto. After stirring at roomtemperature for 12 hours, the precipitated salt was filtered off. Theresulting filtrate was dropped into 1 L of water. The precipitated resinwas separated by filtration, dried under reduced pressure, dissolved intetrahydrofuran, and dropped into 1 L of n-heptane. The precipitatedresin was separated by filtration and dried under reduced pressure togive white powder resin. The yield was 10.5 g. This resin is referred toas resin 12. The resin 12 had a weight-average molecular weight of 9800,a degree of dispersion (Mw/Mn) of 2.21, and a protection degree of 53%.

Resin Synthesis Example 11

10.0 g of the resin 13 (weight-average molecular weight=7640, degree ofdispersion (Mw/Mn)=1.93) was dissolved in 100 mL of tetrahydrofuran, and0.48 g of sodium hydride was added thereto. The mixture was stirred atroom temperature until the solution became uniform, and then 1.26 g ofthe above compound 1 was added dropwise thereto. After stirring at roomtemperature for 12 hours, the precipitated salt was filtered off. Theresulting filtrate was dropped into 1 L of water. The precipitated resinwas separated by filtration, dried under reduced pressure, dissolved intetrahydrofuran, and dropped into 1 L of n-heptane. The precipitatedresin was separated by filtration and dried under reduced pressure togive white powder resin. The yield was 6.0 g. This resin is referred toas resin 14. The resin 14 had a weight-average molecular weight of 9970,a degree of dispersion (Mw/Mn) of 1.70, and a protection degree of30.7%. The absorptivity coefficient was 1.67 μm⁻¹.

Comparative Resin Synthesis Example 1

15.0 g of the resin 13 (weight−average molecular weight=7640, degree ofdispersion (Mw/Mn)=1.93) was dissolved in 100 mL of tetrahydrofuran, and0.88 g of sodium hydride was added thereto. The mixture was stirred atroom temperature until the solution became uniform, and then 1.76 g ofchloromethyl methyl ether (manufactured by Tokyo Kasei Kogyo Co., Ltd.)was added dropwise thereto. After stirring at room temperature for 12hours, the precipitated salt was filtered off. The resulting filtratewas dropped into 1 L of water. The precipitated resin was separated byfiltration, dried under reduced pressure, dissolved in tetrahydrofuran,and dropped into 1 L of n-heptane. The precipitated resin was separatedby filtration and dried under reduced pressure to give white powderresin. The yield was 5.0 g. This resin is referred to as resin 15. Theresin 15 had a weight-average molecular weight of 14000, a degree ofdispersion (Mw/Mn) of 2.14, and a protection degree of 40.7%. Theabsorptivity coefficient was 1.73 μm⁻¹.

Comparative Resin Synthesis Example 2

10.0 g of the resin 13 (weight-average molecular weight=7640, degree ofdispersion (Mw/Mn)=1.93) was dissolved in 100 mL of tetrahydrofuran, and0.48 g of sodium hydride was added thereto. The mixture was stirred atroom temperature until the solution became uniform, and then 1.035 g ofchloromethyl methyl ether (manufactured by Tokyo Kasei Kogyo Co., Ltd.)was added dropwise thereto. After stirring at room temperature for 12hours, the precipitated salt was filtered off. The resulting filtratewas dropped into 1 L of water. The precipitated resin was separated byfiltration, dried under reduced pressure, dissolved in tetrahydrofuran,and dropped into 1 L of n-heptane. The precipitated resin was separatedby filtration and dried under reduced pressure to give white powderresin. The yield was 6.0 g. This resin is referred to as resin 16. Theresin 16 had a weight-average molecular weight of 8850, a degree ofdispersion (Mw/Mn) of 1.76, and a protection degree of 27.7%. Theabsorptivity coefficient was 1.73 μm⁻¹.

The general formulae representing the resins 1 to 16 are shown in thefollowing formulae 14A and 15A:

Example 1

Confirmation of the Light Exposure Resolution of a Positive ResistComposition

The resolution of a positive resist composition using the resin 3 wasconfirmed by exposure to an ArF excimer laser light. The resolution andexposure amount are shown in Table 1. The following acid generator andnitrogen-containing compound besides the resin were used to prepare theresist composition. Resin 3 100 parts by weight Acid generator: TPS-PFBS(triphenyl sulfonium 3.0 parts by weight perfluorobutane sulfonate)Nitrogen-containing compound: triisopropanol 0.1 part by weight amineSolvent: MAK (methyl amyl ketone) 1250 parts by weight

Example 2

Confirmation of the Light Exposure Resolution of a Positive ResistComposition

The resolution of a positive resist using the resin 6 was confirmed byexposure to an ArF excimer laser light. The resolution and exposureamount are shown in Table 1. The following acid generator andnitrogen-containing compound besides the resin were used to prepare theresist composition. Resin 6 100 parts by weight Acid generator: TPS-PFBS3.0 parts by weight Nitrogen-containing compound: triisopropanol 0.1part by weight amine Solvent: MAK 1250 parts by weight

Example 3

Confirmation of the Light Exposure Resolution of a Positive ResistComposition

The resolution of a positive resist using the resin 10 was confirmed byexposure to an ArF excimer laser light. The resolution and exposureamount are shown in Table 1. The following acid generator andnitrogen-containing compound besides the resin were used to prepare theresist composition. Resin 10 100 parts by weight Acid generator:TPS-PFBS 3.0 parts by weight Nitrogen-containing compound:triisopropanol 0.1 part by weight amine Solvent: MAK 1250 parts byweight

Example 4

Confirmation of the Light Exposure Resolution of a Positive ResistComposition

The resolution of a positive resist using the resin 9 was confirmed byexposure to an F₂ excimer laser light. The resolution and exposureamount are shown in Table 1. The following acid generator andnitrogen-containing compound besides the resin were used to prepare theresist composition. Resin 9 100 parts by weight Acid generator: TPS-PFBS3.5 parts by weight Nitrogen-containing compound: triisopropanol 0.1part by weight amine Solvent: PGMEA (propylene glycol monomethyl 1250parts by weight ether acetate)

TABLE 1 Resolution Sensitivity Resist PB/PEB (nm) by (mJ/cm²) bythickness temperature exposure to exposure to (nm) (° C.) ArF and F₂ ArFand F₂ Example 1 196 90/110 130 20 Example 2 170 90/110 130 11 Example 3170 90/110 130 24 Example 4 150 110/110  90 37

Example 5

100 parts by weight of the resin 14 obtained in Resin Synthesis Example11 as component (A), 3.0 parts by weight of triphenyl sulfoniumperfluorobutane sulfonate as component (B), and 0.1 part by weight oftriisopropanol amine as component (C) were dissolved in 1150 parts byweight of propylene glycol monomethyl ether acetate to prepare apositive resist composition.

An organic anti-reflective film composition “AR-19” (trade name,manufactured by Shipley Company) was then applied onto a silicon waferby using a spinner and baked to dry at 215° C. for 60 seconds on a hotplate thereby forming an organic anti-reflective film of 82 nm inthickness. The positive resist composition was then applied by a spinneronto the anti-reflective film and pre-baked (PAB) to dry at 110° C. for90 seconds on a hot plate, whereby a resist layer of 200 nm in thicknesswas formed.

The resist layer was then irradiated selectively via a mask pattern(binary) with an ArF excimer laser (193 nm) by an ArF light exposureapparatus NSR-S302 (NA (numerical aperture)=0.60, ⅔ orbicular zone,manufactured by Nikon Corporation).

The resist layer was then subjected to PEB treatment under conditions of90° C. and 90 seconds, then developed by puddling for 60 seconds with2.38 wt % aqueous tetramethylammonium hydroxide solution at 23° C. toform a resist pattern. As a result, the limit resolution of a line andspace upon exposure to such a quantity of light as to transfer a 130 nmmask at a level of 130 nm was 120 nm. The sensitivity upon formation ofthe 130 nm line and space at 1:1 was 20 mJ/cm².

Example 6

A positive resist composition was prepared to form a resist pattern inthe same manner as in Example 5 except that the amount of the component(B) was changed to 2.0 parts by weight, the PEB conditions were changedto 90° C. and 60 seconds, and the development time was changed to 30seconds. As a result, the limit resolution of a line and space uponexposure to such a quantity of light as to transfer a 130 nm mask at alevel of 130 nm was 110 nm. The sensitivity upon formation of the 130 nmline and space at 1:1 was 52 mJ/cm².

Comparative Example 1

100 parts by weight of the resin 15 obtained in Comparative ResinSynthesis Example 1 as component (A), 3.0 parts by weight of triphenylsulfonium perfluorobutane sulfonate as component (B), and 0.1 part byweight of triisopropanol amine as component (C) were dissolved in 1150parts by weight of propylene glycol monomethyl ether acetate to preparea positive resist composition.

An organic anti-reflective film composition “AR-19” (trade name,manufactured by Shipley Company) was then applied onto a silicon waferby using a spinner and baked to dry at 215° C. for 60 seconds on a hotplate thereby forming an organic anti-reflective film of 82 nm inthickness. The positive resist composition was then applied by a spinneronto the anti-reflective film and pre-baked (PAB) at 110° C. for 90seconds on a hot plate, whereby a resist layer of 200 nm in thicknesswas formed.

The resist layer was then irradiated selectively via a mask pattern(binary) with an ArF excimer laser (193 nm) by an ArF light exposureapparatus NSR-S302 (NA (numerical aperture)=0.60, ⅔ orbicular zone,manufactured by Nikon Corporation).

The resist layer was then subjected to PEB treatment under conditions of90° C. and 90 seconds, then developed by puddling for 60 seconds with2.38 wt % aqueous tetramethylammonium hydroxide solution at 23° C. toform a resist pattern. As a result, the limit resolution of a line andspace upon exposure to such a quantity of light as to transfer a 130 nmmask at a level of 130 nm was 120 nm. The sensitivity upon formation ofthe 130 nm line and space at 1:1 was 20 mJ/cm².

Comparative Example 2

A positive resist composition was prepared to form a resist pattern inthe same manner as in Example 5 except that the amount of the component(B) was changed to 2.0 parts by weight, the PEB conditions were changedto 90° C. and 60 seconds, and the development time was changed to 30seconds, but the resist pattern did not show resolution.

Comparative Example 3

100 parts by weight of the resin 16 obtained in Comparative ResinSynthesis Example 2 as component (A), 3.0 parts by weight of triphenylsulfonium perfluorobutane sulfonate as component (B), and 0.1 part byweight of triisopropanol amine as component (C) were dissolved in 1150parts by weight of propylene glycol monomethyl ether acetate to preparea positive resist composition.

An organic anti-reflective film composition “AR-19” (trade name,manufactured by Shipley Company) was then applied onto a silicon waferby using a spinner and baked by drying at 215° C. for 60 seconds on ahot plate thereby forming an organic anti-reflective film of 82 nm inthickness. The positive resist composition was then applied by a spinneronto the anti-reflective film and pre-baked (PAB) at 110° C. for 90seconds on a hot plate, whereby a resist layer of 200 nm in thicknesswas formed.

The resist layer was then irradiated selectively via a mask pattern(binary) with an ArF excimer laser (193 nm) by an ArF light exposureapparatus NSR-S302 (NA (numerical aperture)=0.60, ⅔ orbicular zone,manufactured by Nikon Corporation).

The resist layer was subjected to PEB treatment under conditions of 90°C. and 90 seconds, then developed by puddling for 60 seconds with 2.38wt % aqueous tetramethylammonium hydroxide solution at 23° C. to form aresist pattern. As a result, the limit resolution of a line and spaceupon exposure to such a quantity of light as to transfer a 130 nm maskat a level of 130 nm was 120 nm. The sensitivity upon formation of the130 nm line and space at 1:1 was 14 mJ/cm².

Comparative Example 4

A positive resist composition was prepared to form a resist pattern inthe same manner as in Example 5 except that the amount of the component(B) was changed to 2.0 parts by weight, the PEB conditions were changedto 90° C. and 60 seconds, and the development time was changed to 30seconds. As a result, the limit resolution of a line and space uponexposure to such a quantity of light as to transfer a 130 nm mask at alevel of 130 nm was 110 nm. The sensitivity upon formation of the 130 nmline and space at 1:1 was 30 mJ/cm².

The absorptivity coefficients for light having a wavelength of 157 nm inResin Synthesis Examples 11 and Resin Comparative Synthesis Examples 1to 2 were measured in the following manner. First, the resin wasdissolved in propylene glycol monomethyl ether acetate (PGMEA), and theresulting resin solution was applied onto a magnesium fluoride wafer andthen heated at 110° C. for 90 seconds to form a resin coating of 200 nmin thickness. The resin coating was irradiated with light having awavelength of 157 nm by a vacuum ultraviolet spectrophotometer VUV-200(manufactured by JASCO Corporation) to determine absorptivitycoefficient (μm⁻¹).

The resolutions in Examples 1 to 3, 5, and 6, and Comparative Examples 1to 4 were confirmed by using an ArF excimer laser (193 nm), and thussignificant difference thereamong was hardly observed. However, whenresolution was confirmed with an F₂ excimer laser (157 nm), each resinused in Examples 1 to 6 had a higher content of fluorine atoms than ineach resin used in Comparative Examples 1 to 4, thus showing highertransparency to an F₂ excimer laser light. Accordingly, each resin inthe Examples can be used preferably in lithography using an F₂ excimerlaser light. As one example, a 90 nm line and space pattern is resolvedin lithography using an F₂ excimer laser light in Example 4.

INDUSTRIAL APPLICABILITY

As described above, the photoresist composition according to the presentinvention is useful for patterning of a semiconductor integrated circuitby lithography, and is suitable for fine patterning with a light sourceof a wavelength of 300 nm or less, especially KrF, ArF, and F₂ excimerlasers, particularly an F₂ excimer laser. The low-molecular compound andhigh-molecular compound of the present invention are useful forconstituting the photoresist composition, and are particularlypreferable in the photoresist composition excellent in transparency infine patterning with a light source of a wavelength of 300 nm or less,especially KrF, ArF, and F₂ excimer lasers, particularly an F₂ excimerlaser.

REFERENCES

-   Patent document 1: International publication WO 00/67072 Pamphlet-   Patent document 2: Japanese Patent Application Laid-open No.    2002-90997-   Patent document 3: International publication WO 02/64648 Pamphlet-   Patent document 4: International publication WO 02/65212 Pamphlet-   Patent document 5: Japanese Patent Application Laid-open No.    2002-333715-   Non-patent document 1: M. K. Crawford, et al., “New Material for 157    nm Photoresists: Characterization and Properties” Proceedings of    SPIE, Vol. 3999, (2000) pp357-364-   Non-patent document 2: Shun-ichi Kodama, et al., “Synthesis of Novel    Fluoropolymer for 157 nm Photoresists by Cyclo-polymerization”    Proceedings of SPIE, Vol. 4690, (2000) pp76-83

1. A photoresist composition comprising: (A) a base resin componenthaving alkali-solubility changed by the action of an acid; and (B) anacid generator for generating an acid by irradiation with radiationrays, wherein the base resin component (A) comprises a compound havingan alkali-soluble site (i), at least a part of the alkali-soluble site(i) is protected with (ii) a halogen atom-containing acetal typedissolution inhibiting group, and the dissolution inhibiting group (ii)is a group dissociable from the alkali-soluble site (i) by an acid. 2.The photoresist composition according to claim 1, wherein thealkali-soluble site (i) is at least one member selected from the groupconsisting of an alcoholic hydroxyl group, a phenolic hydroxyl group,and a hydroxyl group of a carboxyl group.
 3. The photoresist compositionaccording to claim 2, wherein the alcoholic hydroxyl group is afluorine-containing hydroxyl group.
 4. The photoresist compositionaccording to claim 1, wherein the dissolution inhibiting group (ii) is agroup represented by the following general formula (1):—O—C(R¹)(R²)—O—R³  (1) wherein R¹ and R² independently represent ahydrogen atom or a lower alkyl group, and R³ represents ahalogen-containing substituted or unsubstituted hydrocarbon group. 5.The photoresist composition according to claim 4, wherein R³ in thegeneral formula (1) is a group represented by the following generalformula (2):—[C(R⁵)(R⁶)]_(n)—R⁴  (2) wherein R⁴ represents a halogen-containinglinear or cyclic hydrocarbon group, R⁵ and R⁶ independently represent ahydrogen atom or a lower alkyl group, and n is 0 or an integer of 1 to3.
 6. The photoresist composition according to claim 5, wherein R⁴ inthe general formula (2) is a 1-halogen-substituted linear lower alkylgroup.
 7. The photoresist composition according to claim 5, wherein R⁴in the general formula (2) is a halogen-containing cyclic alkyl group.8. The photoresist composition according to claim 7, wherein thehalogen-containing cyclic alkyl group is a halogen-containing norbornylgroup.
 9. The photoresist composition according to claim 5, wherein R⁴in the general formula (2) is a halogen-containing cyclic alkenyl group.10. The photoresist composition according to claim 9, wherein thehalogen-containing cyclic alkenyl group is a halogen-containingnorbornenyl group.
 11. The photoresist composition according to claim 1,wherein the halogen is a fluorine atom.
 12. A low-molecular compound fora photoresist composition, which is a low-molecular compound for anacid-dissociative, dissolution inhibiting agent contained in thephotoresist composition which generates an acid by light exposure andchanges solubility in an alkaline solution by the action of the acid toform a pattern, wherein the low-molecular compound has an alkali-solublesite (i), at least a part of the alkali-soluble site (i) is protectedwith (ii) a halogen atom-containing acetal type dissolution inhibitinggroup, and the dissolution inhibiting group (ii) is a group dissociablefrom the alkali-soluble site (i) by an acid.
 13. The low-molecularcompound for a photoresist composition according to claim 12, whereinthe alkali-soluble site (i) is at least one member selected from thegroup consisting of an alcoholic hydroxyl group, a phenolic hydroxylgroup, and a hydroxyl group of a carboxyl group.
 14. The low-molecularcompound for a photoresist composition according to claim 13, whereinthe alcoholic hydroxyl group is a fluorine-containing alcoholic hydroxylgroup.
 15. The low-molecular compound for a photoresist compositionaccording to claim 12, wherein the halogen atom-containing acetal typeacid-dissociative, dissolution inhibiting group (ii) is a grouprepresented by the following general formula (1):—O—C(R¹)(R²)—O—R³  (1) wherein R¹ and R² independently represent ahydrogen atom or a lower alkyl group, and R³ represents ahalogen-containing substituted or unsubstituted hydrocarbon group. 16.The low-molecular compound for a photoresist composition according toclaim 15, wherein R³ in the general formula (1) is a group representedby the following general formula (2):—[C(R⁵)(R⁶)]_(n)—R⁴  (2) wherein R⁴ represents a halogen-containinglinear or cyclic hydrocarbon group, R⁵ and R⁶ independently represent ahydrogen atom or a lower alkyl group, and n is 0 or an integer of 1 to3.
 17. The low-molecular compound for a photoresist compositionaccording to claim 16, wherein R⁴ in the general formula (2) is a1-halogen-substituted linear lower alkyl group.
 18. The low-molecularcompound for a photoresist composition according to claim 16, wherein R⁴in the general formula (2) is a halogen-containing cyclic alkyl group.19. The low-molecular compound for a photoresist composition accordingto claim 18, wherein the halogen-containing cyclic alkyl group is ahalogen-containing norbornyl group.
 20. The low-molecular compound for aphotoresist composition according to claim 16, wherein R⁴ in the generalformula (2) is a halogen-containing cyclic alkenyl group.
 21. Thelow-molecular compound for a photoresist composition according to claim20, wherein the halogen-containing cyclic alkenyl group is ahalogen-containing norbornenyl group.
 22. The low-molecular compound fora photoresist composition according to claim 12, wherein the halogen isa fluorine atom.
 23. A high-molecular compound for a photoresistcomposition, which is a high-molecular compound for a base resincomponent constituting a photoresist composition which generates an acidby light exposure and changes alkali-solubility by the action of theacid to form a pattern, wherein the high-molecular compound has analkali-soluble site (i), at least a part of the alkali-soluble site (i)is protected with (ii) a halogen atom-containing acetal type dissolutioninhibiting group, and the dissolution inhibiting group (ii) is a groupdissociable from the alkali-soluble site (i) by an acid.
 24. Thehigh-molecular compound for a photoresist composition according to claim23, wherein the alkali-soluble site (i) is at least one member selectedfrom the group consisting of an alcoholic hydroxyl group, a phenolichydroxyl group, and a hydroxyl group of a carboxyl group.
 25. Thehigh-molecular compound for a photoresist composition according to claim24, wherein the alcoholic hydroxyl group is a fluorine-containingalcoholic hydroxyl group.
 26. The high-molecular compound for aphotoresist composition according to claim 23, wherein the halogenatom-containing acetal type acid-dissociative, dissolution inhibitinggroup (ii) is a group represented by the following general formula (1):—O—C(R¹)(R²)—O—R³  (1) wherein R¹ and R² independently represent ahydrogen atom or a lower alkyl group, and R³ represents ahalogen-containing substituted or unsubstituted hydrocarbon group. 27.The high-molecular compound for a photoresist composition according toclaim 26, wherein R³ in the general formula (1) is a group representedby the following general formula (2):—[C(R⁵)(R⁶)]_(n)—R⁴  (2) wherein R⁴ represents a halogen-containinglinear or cyclic hydrocarbon group, R⁵ and R⁶ independently represent ahydrogen atom or a lower alkyl group, and n is 0 or an integer of 1 to3.
 28. The high-molecular compound for a photoresist compositionaccording to claim 27, wherein R⁴ in the general formula (2) is a1-halogen-substituted linear lower alkyl group.
 29. The high-molecularcompound for a photoresist composition according to claim 27, wherein R⁴in the general formula (2) is a halogen-containing cyclic alkyl group.30. The high-molecular compound for a photoresist composition accordingto claim 29, wherein the halogen-containing cyclic alkyl group is ahalogen-containing norbornyl group.
 31. The high-molecular compound fora photoresist composition according to claim 27, wherein R⁴ in thegeneral formula (2) is a halogen-containing cyclic alkenyl group. 32.The high-molecular compound for a photoresist composition according toclaim 31, wherein the halogen-containing cyclic alkenyl group is ahalogen-containing norbornenyl group.
 33. The high-molecular compoundfor a photoresist composition according to claim 23, wherein the halogenis a fluorine atom.